Typical Hydraulic Valve Lifter Operation; Lubrication System - Lincoln Continental 1964 Shop Manual

8-20
GROUP 8-ENGINE
(140)
VALVE OPEN
VALVE CLOSED
FIG. 5-
Typi,al Hydrauli' Valve
Lifter Operation
and washer, located within the rota-
tor, causes a constant speed rotation.
The valve rotator eliminates the need
for a conventional valve spring re-
tainer and sleeve for the exhaust
valves.
The push rods have a radius at
each end and are oil cushioned at the
rocker arm and valve lifter.
The heavy gauge valve springs
are color coded for identification
purposes.
The rocker arms are a non-adjust-
ing type. Each rocker arm and shaft
assembly is held in position on the
cylinder head by four rocker arm
supports and retaining bolts. The
valve rocker arm covers and gaskets
are held in position by bolts, and
reinforcements (washers), located
around the cover rim. A comb-type
bracket is located on the top of each
cover for positive alignment of the
spark plug high tension wiring.
The camshaft is supported by five
replaceable bearing inserts. The in-
side diameters of the bearings are of
a step design. The largest inside
diameter is found in the front bear-
ing. The inside diameters of the
bearings decrease 0.015 inch in size
per bearing, from the front bearing
toward the rear.
The camshaft is also of step de-
sign, the largest journal 'outside
diameter is found at the front jour-
nal. The journals, from the front to
rear, decrease 0.015 inch in size per
journal.
A1245-B
FIG.
6-Lubri,ation System
The camshaft is driven by the
crankshaft sprocket, timing chain,
and timing gear that has nylon teeth.
The timing gear and camshaft eccen-
tric is bolted to the camshaft.
Hydraulic ·valve lifters are used in
the engine. The valve lifters are
housed in bores located in the cylin-
der block valve lifter chamber. The
valve lifters operate directly on the
camshaft lobes, thereby transmitting
the thrust of the camshaft lobes, by
the means of hydraulic pressure, to
the push rods which actuate the
valve train. Figure 5 shows the vari-
ous components and operation of a
hydraulic valve lifter.
When either an exhaust valve or
an intake valve is closed, the actuat-
ing valve lifter is on the base circle
(lowest position) of the camshaft
lobe.
When the valve lifter is in this
position, the lifter plunger spring
expands. This action forces the lifter
plunger and valve push rod upward,
forcing the valve end of the rocker
arm to maintain solid contact with
the valve (zero valve lash). In this
position, the oil hole in the lifter
body and plunger is indexed with
the oil gallery in the cylinder block.
As the lifter plunger moves up-
ward, the volume of the compression
chamber is increased, resulting in
reduced oil pressure in the compres-
sion chamber. Therefore, to equalize
the resulting pressure differential be-
tween the supply chamber and the
compression chamber, the disc valve
moves off its seat and permits oil to
flow from the supply chamber to the
compression chamber. When the
compression chamber becomes filled
with oil, the pressures in the two
chambers are equalized. The oil flow
ceases and the disc valve spring seats
the disc valve and closes the disc
valve port.
As the camshaft rotates, the lifter
assembly is raised by the camshaft
lobe. This increases the push rod
force against the lifter plunger and
hydraulic pressure immediately
builds up in the compression cham-
ber until it acts as a solid member
of the valve operating mechanism.
The lifter then becomes a hydraulic
ram which forces the valve in the
cylinder head to open. During this
period, a slight leakage of oil past
the plunger occurs (calibrated leak
down rate).
As the high point of the camshaft
lobe rotates and passes by the foot
of the valve lifter, the valve in the
cylinder head seats and the valve
lifter assembly is forced downward.
Reduced force on the lifter plunger
at this time relieves the pressure on
the lifter plunger and it is free to
be moved upward by the plunger
spring. This action allows oil to flow
once again through the indexed oil
holes in the lifter body and plunger.
The operating cycle is completed
for each revolution of the camshaft.
Zero clearance (lash) in the valve